About this tool
This calculator computes compound growth on a starting amount, factoring in the compounding frequency you choose and any regular contributions added along the way. All math runs in your browser.
How to use the Compound Interest Calculator
- Enter your Starting amount and the Annual interest rate (%).
- Set the Years and the Compounding frequency: Annually, Quarterly, Monthly or Daily.
- Optionally add a Regular contribution and choose its frequency, Monthly or Annually. Each deposit is added at the end of its month or year, after that period’s interest.
- Read the Final balance, Total contributed (starting amount plus deposits) and Interest earned. They update as you type.
Common use cases
- Estimating how a savings or investment balance could grow over time
- Comparing how different compounding frequencies affect the same rate
- Seeing the impact of adding regular contributions versus a one-time deposit
- Understanding roughly how much of a future balance is contributions versus interest
Why compounding frequency matters
A 7% annual rate compounded monthly grows slightly faster than the same 7% compounded annually, because interest starts earning its own interest sooner — each month's interest gets added to the balance and starts generating more interest right away, rather than waiting a full year. The difference is usually small for typical rates and timeframes, but it grows more noticeable over longer periods or higher rates.
Things to watch out for
This tool calculates pure mathematical compound growth based on a fixed rate you enter — real investments don't grow at a perfectly steady rate, and this doesn't account for taxes, fees, or inflation, all of which reduce real-world returns. Treat the result as an illustration of how compounding works, not a guaranteed projection or financial advice; actual investment returns vary and this tool isn't a substitute for consulting a financial professional for real planning decisions.
The rule of 72 and a worked comparison
A quick check on any result is the rule of 72: divide 72 by the annual rate to estimate how many years it takes money to double. At 7% that is about 10.3 years. As a worked example, $10,000 at 7% for 20 years grows to $38,696.84 when compounded yearly and $40,387.39 when compounded monthly. The extra $1,690.55 comes only from the more frequent compounding. With regular deposits, $1,000 at 7% compounded monthly for 10 years with $100 added every month gives a final balance of $19,318.14: $13,000.00 contributed and $6,318.14 in interest. Real returns vary year to year, so treat any single rate as an assumption, not a promise.
Frequently asked questions
Simple interest is calculated only on the original principal, so it grows by the same dollar amount every period. Compound interest is calculated on the principal plus all previously earned interest, so the growth accelerates over time.
It's how often interest is calculated and added to the balance — annually, monthly, or daily, for example. More frequent compounding produces slightly more growth for the same stated annual rate, since interest starts earning its own interest sooner.
No — this calculates pure compound growth based on the numbers you enter. Real-world returns are often reduced by taxes, account fees, or inflation, none of which are factored in here.
This calculator works in monthly steps: interest builds up each month and is added to the balance every 12 months (Annually), every 3 months (Quarterly) or every month (Monthly). Daily cannot compound more often than one step, so it gives exactly the same result as Monthly. For $10,000 at 7% over 20 years both show $40,387.39, while true compounding 365 times a year would reach about $40,546.56.